On July 11, 1988, between 2207 and 2213 UTC (16:07-16:13 MDT), four successive United flights had inadvertent encounters with microburst windshear conditions while on final approach to Denver Stapleton Airport, each resulting in a missed approach, but uneventful arrival. A fifth flight executed a missed approach without encountering the phenomena. All of the flight crews were trained to use the resources of the Windshear Training Aid. There was no damage to aircraft and no passenger injuries. At the time the aircraft encountered the microburst, the Terminal Doppler Weather Radar (TDWR) operations test and experiment was in progress and detected divergent flow that intersected the operating zones for the approach runways. The radar used to test the TDWR algorithm was the MIT Lincoln Lab. 10 cm Doppler radar. This study outlines the technical details of the encounter, as well as describes insights gained from this confrontation that should be applied to future investigations of aircraft encountering windshear. Information from several sources includes flight crew comments, air traffic control operations and surveillance radar data, flight data recorders, data from the TDWR and the Low-Level Wind Shear Alert System (LLWAS), technical details of the event meteorology, and data from the Terminal Area Simulation System (TASS). Aviation safety.